Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
  • G01F1/00—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow
  • G01F1/76—Devices for measuring mass flow of a fluid or a fluent solid material
  • G01F1/78—Direct mass flowmeters
  • G01F1/80—Direct mass flowmeters operating by measuring pressure, force, momentum, or frequency of a fluid flow to which a rotational movement has been imparted
  • G01F1/84—Coriolis or gyroscopic mass flowmeters
  • G01F1/8409—Coriolis or gyroscopic mass flowmeters constructional details
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
  • G01D3/00—Indicating or recording apparatus with provision for the special purposes referred to in the subgroups
  • G01D3/028—Indicating or recording apparatus with provision for the special purposes referred to in the subgroups mitigating undesired influences, e.g. temperature, pressure
  • G01D3/036—Indicating or recording apparatus with provision for the special purposes referred to in the subgroups mitigating undesired influences, e.g. temperature, pressure on measuring arrangements themselves
  • G01D3/0365—Indicating or recording apparatus with provision for the special purposes referred to in the subgroups mitigating undesired influences, e.g. temperature, pressure on measuring arrangements themselves the undesired influence being measured using a separate sensor, which produces an influence related signal
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
  • G01F1/00—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow
  • G01F1/76—Devices for measuring mass flow of a fluid or a fluent solid material
  • G01F1/78—Direct mass flowmeters
  • G01F1/80—Direct mass flowmeters operating by measuring pressure, force, momentum, or frequency of a fluid flow to which a rotational movement has been imparted
  • G01F1/84—Coriolis or gyroscopic mass flowmeters
  • G01F1/8409—Coriolis or gyroscopic mass flowmeters constructional details
  • G01F1/8413—Coriolis or gyroscopic mass flowmeters constructional details means for influencing the flowmeter's motional or vibrational behaviour, e.g., conduit support or fixing means, or conduit attachments
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
  • G01F1/00—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow
  • G01F1/76—Devices for measuring mass flow of a fluid or a fluent solid material
  • G01F1/78—Direct mass flowmeters
  • G01F1/80—Direct mass flowmeters operating by measuring pressure, force, momentum, or frequency of a fluid flow to which a rotational movement has been imparted
  • G01F1/84—Coriolis or gyroscopic mass flowmeters
  • G01F1/8409—Coriolis or gyroscopic mass flowmeters constructional details
  • G01F1/8422—Coriolis or gyroscopic mass flowmeters constructional details exciters
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
  • G01F1/00—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow
  • G01F1/76—Devices for measuring mass flow of a fluid or a fluent solid material
  • G01F1/78—Direct mass flowmeters
  • G01F1/80—Direct mass flowmeters operating by measuring pressure, force, momentum, or frequency of a fluid flow to which a rotational movement has been imparted
  • G01F1/84—Coriolis or gyroscopic mass flowmeters
  • G01F1/8409—Coriolis or gyroscopic mass flowmeters constructional details
  • G01F1/8436—Coriolis or gyroscopic mass flowmeters constructional details signal processing
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
  • G01F1/00—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow
  • G01F1/76—Devices for measuring mass flow of a fluid or a fluent solid material
  • G01F1/78—Direct mass flowmeters
  • G01F1/80—Direct mass flowmeters operating by measuring pressure, force, momentum, or frequency of a fluid flow to which a rotational movement has been imparted
  • G01F1/84—Coriolis or gyroscopic mass flowmeters
  • G01F1/845—Coriolis or gyroscopic mass flowmeters arrangements of measuring means, e.g., of measuring conduits
  • G01F1/8468—Coriolis or gyroscopic mass flowmeters arrangements of measuring means, e.g., of measuring conduits vibrating measuring conduits
  • G01F1/849—Coriolis or gyroscopic mass flowmeters arrangements of measuring means, e.g., of measuring conduits vibrating measuring conduits having straight measuring conduits
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
  • G01F15/00—Details of, or accessories for, apparatus of groups G01F1/00 - G01F13/00 insofar as such details or appliances are not adapted to particular types of such apparatus
  • G01F15/02—Compensating or correcting for variations in pressure, density or temperature
  • G01F15/022—Compensating or correcting for variations in pressure, density or temperature using electrical means
  • G01F15/024—Compensating or correcting for variations in pressure, density or temperature using electrical means involving digital counting
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N11/00—Investigating flow properties of materials, e.g. viscosity, plasticity; Analysing materials by determining flow properties
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N11/00—Investigating flow properties of materials, e.g. viscosity, plasticity; Analysing materials by determining flow properties
  • G01N2011/0006—Calibrating, controlling or cleaning viscometers
  • G01N2011/0013—Temperature compensation
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N9/00—Investigating density or specific gravity of materials; Analysing materials by determining density or specific gravity

Definitions

• the invention relates to a process measuring device for measuring at least one physical process variable, in particular a mass flow, a density, a viscosity, a pressure or the like, of a medium held in a process container or flowing in a process line.
• the process variables to be recorded in each case can be, for example, a mass flow rate, a density, a viscosity, a fill or a limit level, a pressure or a temperature or the like, of a liquid, powder, vapor or gaseous process medium, that in an appropriate process container, such as a pipeline or a tank.
• the process measuring device has a corresponding, mostly physical-electrical, measuring sensor, which is inserted into a wall of the container carrying the process medium or in the course of a process line leading the process medium and which is used to generate at least one, in particular electrical, measurement signal that represents the primary detected process variable as precisely as possible.
• the measuring sensor is also connected to a corresponding measuring device electronics, in particular also a further processing or evaluation of the at least one measuring signal.
• process measuring devices of the type described are usually connected to one another and / or to corresponding process control computers via a data transmission system connected to the measuring device electronics, wherever the measured value signals e.g. Send via (4 mA to 20 mA) current loop and / or via digital data bus.
• the data transmission systems used here especially serial, fieldbus systems, e.g. PROFIBUS-PA, FOUNDATION FIELDBUS as well as the corresponding transmission protocols.
• the transmitted measured value signals can be further processed and e.g. visualized on monitors and / or in control signals for process actuators, e.g. Solenoid valves, electric motors etc., are converted.
• such process measuring devices further comprise an electronics housing which, e.g. proposed in US-A 63 97 683 or WO-A 00 36 379, arranged away from the field measurement device and can only be connected to it via a flexible line or that, e.g. also shown in EP-A 903 651 or EP-A 1 008 836, is arranged directly on the sensor or a sensor housing housing the sensor separately.
• an electronics housing which, e.g. proposed in US-A 63 97 683 or WO-A 00 36 379, arranged away from the field measurement device and can only be connected to it via a flexible line or that, e.g. also shown in EP-A 903 651 or EP-A 1 008 836, is arranged directly on the sensor or a sensor housing housing the sensor separately.
• the electronics housing as shown for example in EP-A 984248, US-A 45 94 584, US-A 47 16 770 or US-A 63 52 000, then often also serves to serve some mechanical components of the sensor to record, such as operationally deforming membrane, rod, sleeve or tubular deformation or vibration bodies under mechanical influence, cf. also US-B 63 52 000 mentioned at the beginning.
• At least one measuring tube for guiding the medium, in particular the flow
• a sensor arrangement which delivers measurement signals and which has at least one first and a second sensor element which reacts primarily to the physical process variable, in particular also changes in the process variable, and delivers at least one first and second measurement signal influenced by the physical process variable,
• the measuring device electronics deliver at least one excitation signal which serves to control the vibration exciter, so that the measuring tube is made to vibrate at least temporarily during operation,
• the measurement signals supplied by sensor elements from the process medium influenced mechanical vibrations of the vibrating measuring tube.
• such a process measuring device of the vibration type further comprises a measuring sensor housing housing the measuring tube with the vibration exciters and sensors arranged thereon as well as any other components of the measuring sensor.
• the measuring device electronics also determines a phase difference between the two measuring signals supplied by the sensor elements, here vibration signals, and gives the measuring device electronics to them Output a measured value signal, which, corresponding to the time course of the phase difference, represents a measured value of the mass flow.
• process measuring devices of the type described, in particular on their respective measuring transducers, in addition to the process variables described above, which are primarily to be recorded, can also include other physical variables, especially those which cannot be influenced, in particular. a process or medium temperature.
• a thermally variable expansion of the measuring tube can also lead to the sensor not only being sensitive to the primary measured variables, e.g. has a mass flow rate, a density and / or a viscosity, and also a cross sensitivity to a temperature distribution currently prevailing in the sensor.
• the sensor is practically detuned.
• the measured value signal supplied by the measuring device electronics can also be incorrect if this "detuning" is not taken into account.
• Coriolis mass flow measuring devices or Coriolis mass flow / density measuring devices therefore usually also have at least one temperature sensor, e.g. provided for measuring the temperature of the measuring tube or a measuring tube environment in the sensor arrangement, cf. see also US-A 53 59 881, US-A 56 87 100 or WO-A 88 02 476.
• a temperature sensor for example a Pt100, a Pt1000 or a thermocouple, attached to a curved measuring tube, is first used to match a temperature of the measuring medium. Electrical temperature measurement signal generated. This is then in the measuring device electronics by multiplication with constant, time-invariant coefficients in a correction factor taking into account the influences of the measured temperature on the elasticity module converted and allowed to flow into the correction of the measured value signal, for example a mass flow and / or a density signal. Appropriate digital signal filters can be used to smooth the temperature measurement signal or to improve its signal-to-noise ratio, as suggested, for example, in WO-A 88 02 476.
• process measuring devices of the vibration type with a curved measuring tube In addition to such process measuring devices of the vibration type with a curved measuring tube, process measuring devices of the vibration type with a single straight measuring tube or also with two measuring tubes are also known to the person skilled in the art, cf. see in particular US-A 45 24 610, US-A 47 68 384, US-A 60 06 609, WO-A 00 144485 or WO-A 01 02816.
• process measuring devices with a straight one Measuring tube is usually also provided in the transducer, in particular a vibratingly suspended in the transducer housing, fixed to the measuring tube support element for holding the vibration exciter and the sensor elements, which also serves to decouple the vibrating measuring tube from the connected pipeline.
• the carrier element can e.g. be designed as a tubular compensation cylinder or box-shaped support frame arranged coaxially to the measuring tube.
• process measuring devices of the vibration type with straight measuring tube or straight measuring tubes react to temperature changes not only with the aforementioned modulus of elasticity, but also cause temperature-related changes in mechanical stresses within the measuring tube and possibly also within the carrier element and / or the sensor housing changes in the sensitivity of the sensor to the primary process variables.
• Such temperature-related mechanical stresses can have various causes, which can occur alone or in connection with one another. Even if the measuring tube and carrier element or sensor housing have essentially the same temperatures, temperature-dependent mechanical stresses can occur if the carrier tube and vibrating system are made of different materials with different materials There are coefficients of thermal expansion. Such temperature influences have an even greater effect on the measurement result if the temperature of the measuring tube is different from the temperature of the carrier tube. This is particularly the case if process medium whose temperature is different from the ambient temperature is to be measured. In the case of very hot or very cold process media, there can be a very large temperature gradient between the carrier element or the sensor housing and the measuring tubes.
• Measures to compensate for such temperature influences that change the sensitivity of the measuring sensor to the primary process variables are described, for example, in US Pat. No. 4,768,384, US Pat. No. 5,231,884 or WO-A 01 02816.
• the influence of temperature-dependent expansions or voltages of the sensor housing on the measured value signal is compensated for by the fact that another, the influences of the measured temperature on the expansion or the voltage distribution in the sensor Correction factor is taken into account in the measuring device electronics and is incorporated into the measured value signal. To form this correction factor, each of the temperature signals is multiplied simultaneously and without delay by again constant coefficients and possibly also by itself.
• the temperature distribution during operation of process measuring devices of the type described can, on the one hand, be subject to considerable fluctuations, in particular due to a temperature of the fluid which is usually not constant, and thus within the process measuring device, in particular also within the sensor, repeated dynamic compensation processes with regard to the temperature distribution can be recorded.
• these temporal changes in the temperature distribution due to different specific temperature conductivities or heat capacities of individual components of the measuring sensor, e.g. the measuring tube or the measuring sensor housing, can reach the individual components of the measuring sensor, which also determine the sensitivity of the measuring sensor, with different rapidity, so that also the temperature profiles or gradients detected by means of two or more temperature sensors can be subject to dynamic changes.
• transient transition areas of the temperature distribution can last from a few minutes to a few hours and that during this often quite long period of the transient state of the temperature distribution Influences of the locally recorded temperatures on the measurement signal or the measurement signals can also change in relation to one another.
• One way of reducing such errors in the measurement signal can be with such sensors with a vibrating measuring tube, e.g. consist in installing a large number of temperature sensors distributed along the measuring tube and along the measuring sensor housing and / or along the support element, if any, for the single measuring tube.
• an increase in the number of temperature sensors can also lead to an increased probability of failure of the sensor arrangement itself, in particular when the temperature sensors are fixed to components that vibrate at high frequency during operation, for example the measuring tube or a support element designed as a counter-oscillator.
• the invention consists in a process measuring device for measuring at least one physical process variable, in particular a mass flow rate, a density, a viscosity, a pressure or the like, of a medium held in a process container or flowing in a process line, which measuring device comprises :
• Process variable influenced first measurement signal provides, and in addition arranged at least a first in the sensor
• Has temperature sensor which locally detects a first temperature in the sensor and which at least one the first by means of the at least one temperature sensor
• a measuring device electronics which, using at least the first measurement signal and using a first correction value for the at least first measurement signal, at least one the physical variable at the moment representative measured value, in particular a mass flow measured value, a density measured value, a viscosity measured value or a pressure measured value,
• the measuring device electronics determine the first correction value during operation on the basis of a time course of the at least first temperature measurement signal in that temperature values detected in the past by means of the first temperature sensor are also taken into account.
• the measuring device electronics respond in operation to a change in the first temperature measurement signal corresponding to a change in the first temperature with a time delay with a change in the first correction value.
• the sensor arrangement has at least one second temperature sensor arranged in the measuring sensor, in particular at a distance from the first temperature sensor, which locally detects a second temperature in the measuring sensor, and
• the sensor arrangement delivers at least one second temperature measurement signal representing the second temperature by means of the second temperature sensor.
• the measuring device electronics also determine the first correction value using the second temperature measurement signal.
• the measuring device electronics determine a second correction value on the basis of a time course of at least the second temperature measuring signal and the measuring device electronics also generates the measured value using the second correction value.
• the measuring device electronics comprise a filter stage for generating the at least first correction value, the first temperature measurement signal being fed to a first signal input of the filter stage.
• the filter stage has a first A / D converter for the first temperature measurement signal, which converts this into a first digital signal.
• the filter stage comprises a first digital filter for the first digital signal.
• the first digital filter is a recursive filter.
• the first digital filter is a non-recursive filter.
• the first digital filter supplies the first correction value to a first signal output of the filter stage.
• the filter stage also serves to generate the second correction value, the second temperature measurement signal being fed to a second signal input of the filter stage, and the filter stage has a second A / D converter for the second temperature measurement signal, which converts this into a second digital signal.
• the filter stage comprises a second digital filter for the second digital signal.
• the measuring sensor comprises at least one measuring tube for guiding the medium, in particular flowing.
• the sensor comprises a sensor housing which at least partially surrounds the measuring tube.
• At least one of the two temperature sensors is fixed to the sensor housing or at least arranged in the vicinity thereof.
• the senor further comprises a vibration exciter for driving the measuring tube, which is electrically connected to the measuring device electronics and acts mechanically on the measuring tube, in particular electro-dynamic or electromagnetic, and supplies the measuring device electronics, at least one of them Controlling the excitation signal serving to excite the vibration, so that the measuring tube vibrates at least temporarily during operation.
• a vibration exciter for driving the measuring tube, which is electrically connected to the measuring device electronics and acts mechanically on the measuring tube, in particular electro-dynamic or electromagnetic, and supplies the measuring device electronics, at least one of them Controlling the excitation signal serving to excite the vibration, so that the measuring tube vibrates at least temporarily during operation.
• the first sensor element reacts, in particular on the inlet or outlet side, to vibrations of the measuring tube and represents the measuring signal supplied by the first sensor element from the process medium, which influences the mechanical vibrations of the vibrating measuring tube.
• the measuring sensor comprises a carrier element, in particular suspended in the measuring sensor housing, which is fixed to the measuring tube, for holding the vibration exciter and at least the first sensor element.
• At least one temperature sensor is fixed on the carrier element or at least arranged in the vicinity thereof.
• the sensor arrangement has at least one second sensor element that reacts primarily to the physical process variable and supplies the sensor arrangement by means of the second Sensor element at least one second measurement signal influenced by the physical process variable, the measuring device electronics also generating the measurement value using the second measurement signal.
• a basic idea of the invention is, on the one hand, to determine the instantaneous sensitivity of the measuring sensor to the process variable to be measured as a function of its instantaneous internal temperature distribution and to compensate for the measuring signals affected accordingly.
• the object of the invention is to use the temperatures measured in the past to estimate with sufficient accuracy the temperature distribution currently effective for the sensitivity in the sensor, in particular also using as few temperature sensors as possible.
• Another advantage of the invention in addition to the low circuit complexity for the temperature measurement, is that more degrees of freedom are created for the positioning of the temperature sensors within the sensor, since the respective position of the temperature sensor is now included in the correction when evaluating the temperature measurement signal supplied in each case can be left.
• the temperature sensors can be optimally arranged, particularly from an assembly and / or wiring perspective.
• FIG. 1 shows a perspective side view of a process measuring device
• FIG. 2 shows, in the manner of a block diagram, a measuring device electronics suitable for the process measuring device according to FIG. 1 coupled with a measuring sensor of the Vibrationjs type
• Fig. 3 shows partially sectioned an embodiment of one for the
• Fig. 4 shows the sensor of Fig. 2 in perspective in a second
• Fig. 5 shows an embodiment of an electromechanical
• FIG. 6 shows, in the manner of a block diagram, an evaluation circuit suitable for the measuring device electronics of FIG. 2,
• Fig. 7 shows schematically an example of possible temperature profiles within the sensor of Fig. 2 and
• Fig. 7 shows an embodiment of the block diagram
• 1 and 2 is an embodiment of a process measuring device, for example a Coriolis mass flow meter, a density measuring device and / or a process measuring device 1 with a, preferably housed within a sensor housing 100, sensor 10 of the vibration type as well as shown in an electronics housing 200, in which a measuring device electronics 50, which is electrically connected to the measuring sensor 10, is accommodated.
• a process measuring device for example a Coriolis mass flow meter, a density measuring device and / or a process measuring device 1 with a, preferably housed within a sensor housing 100, sensor 10 of the vibration type as well as shown in an electronics housing 200, in which a measuring device electronics 50, which is electrically connected to the measuring sensor 10, is accommodated.
• the process measuring device 1 is used to record a process variable, for example a mass flow rate, a density and / or a viscosity, of a fluid flowing in a pipeline and to represent it in a measured value signal currently representing this process variable; the pipeline is not shown here for reasons of clarity.
• the sensor 10 comprises a measuring tube 13, which is preferably vibrated in operation in a bending mode so that such reaction forces, such as Coriolis forces, acceleration forces and / or friction forces, of sufficient magnitude are generated in the fluid flowing therethrough are dependent on the process variable and which have a retroactive effect on the sensor 10 in a measurable, that is to say sensor-detectable and electronically evaluable, manner.
• the measuring sensor 10 comprises at least one measuring tube 13 having an inlet end 11 and an outlet end 12 of predeterminable measuring tube lumen 13A, which can be elastically deformed during operation, and of a predeterminable nominal diameter.
• Elastic deformation of the measuring tube lumen 13A means here that in order to generate the above-mentioned, fluid-internal and therefore fluid-describing reaction forces, a spatial shape and / or a spatial position of the measuring tube lumen 13A is changed cyclically, especially periodically, within a range of elasticity of the measuring tube 13 , see. e.g. US-A 48 01 897, US-A 56 48 616, US-A 57 96 011 or US-A 60 06 609.
• the measuring tube e.g. shown in EP-A 1 260 798, for example also be curved.
• transducer arrangements serving as sensors 10 are e.g. in US-A 53 01 557, US-A 53 57 811, US-A 55 57 973, US-A 56 02 345, US-A 56 48 616 or US-A 57 96 011 ,
• Titanium alloys are particularly suitable as material for the straight measuring tube 13 in FIGS. 3 and 4.
• others can also be used for such materials, in particular also used for curved measuring tubes, such as stainless steel, tantalum or zirconium etc. are used.
• the measuring tube 13 which communicates in the usual way on the inlet side and outlet side with the pipeline supplying or discharging the fluid, is in a rigid, in particular flexurally and torsionally rigid, support frame 14 enveloped by the sensor housing 100 clamped to vibrate.
• the support frame 14 is fixed on the measuring tube 13 on the inlet side by means of an inlet plate 213 and on the outlet side by means of an outlet plate 223, the latter both being pierced by corresponding extension pieces 131, 132 of the measuring tube 13. Furthermore, the support frame 14 has a first side plate 24 and a second side plate 34, which two side plates 24, 34 are each fixed to the inlet plate 213 and to the outlet plate 223 in such a way that they run practically parallel to the measuring tube 13 and are spaced apart therefrom are arranged, cf. Fig. 3. Thus, facing side surfaces of the two side plates 24, 34 are also parallel to each other.
• a longitudinal rod 25 is fixed to the side plates 24, 34, spaced from the measuring tube 13, which serves as a balancing mass which counteracts the vibrations of the measuring tube 13.
• the longitudinal rod 25 extends, as shown in FIG. 4, practically parallel to the entire oscillatable length of the measuring tube 13; however, this is not mandatory, the longitudinal bar 25 can of course also be made shorter, if necessary.
• the support frame 14 with the two side plates 24, 34, the inlet plate 213, the outlet plate 223 and the longitudinal rod 25 thus has a longitudinal center of gravity which runs practically parallel to a measuring tube central axis 13B virtually connecting the inlet end 11 and the outlet end 12.
• the measuring tube 13 has a first flange 19 on the inlet side and a second flange 20 on the outlet side, cf. Fig. 1; instead of the flanges 19, 20, e.g. other pipe connection pieces for detachable connection to the pipe, such as the so-called Triciamp connections indicated in FIG. 3. If necessary, the measuring tube 13 can also be connected directly to the pipeline, e.g. be connected by means of welding or brazing etc.
• the measuring tube 13 is vibrated in the operation of the measuring sensor 10, driven by an electromechanical excitation arrangement 16 coupled to the measuring tube, at a predefinable oscillation frequency, in particular a natural resonance frequency, in the so-called useful mode and is thus elastically deformed in a predefinable manner.
• a predefinable oscillation frequency in particular a natural resonance frequency
• this resonance frequency also depends on the current density of the fluid.
• the vibrating measuring tube 13 is spatially, in particular laterally, deflected from a static idle position, as is customary in such transducer arrangements of the bending vibration type;
• a transducer arrangement of the peristaltic radial vibration type serves as the measuring transducer 10, as described, for example, in the mentioned WO-A 95/16 897 and the cross section of the vibrating measuring tube is symmetrically deformed in the usual manner, the measuring tube longitudinal axis remains in their static rest position.
• the excitation arrangement 16 is used to generate an excitation force F exc acting on the measuring tube 13 by converting an electrical excitation power P exc fed in by the measuring device electronics 50.
• the excitation power P exc When excited at a natural resonance frequency, the excitation power P exc practically only serves to compensate for the power component extracted from the vibration system via mechanical and fluid-internal friction. To achieve the highest possible efficiency, the excitation power P exc is therefore set as precisely as possible so that essentially the vibrations of the measuring tube 13 in the desired useful mode, for example that of a basic resonance frequency, are maintained.
• the excitation arrangement 16 For the purpose of transmitting the excitation force F exc to the measuring tube 13, the excitation arrangement 16, as shown in FIG. 5, has a rigid, electromagnetically and / or electrodynamically driven lever arrangement 15 with a cantilever 154 fixed to the measuring tube 13 and with a yoke 163 on.
• the yoke 163 is also fixed to one end of the arm 154 at a distance from the measuring tube 13, in such a way that it is arranged above the measuring tube 13 and transversely to it.
• a boom 154 e.g. serve a metallic disc which receives the measuring tube 13 in a bore.
• a metallic disc which receives the measuring tube 13 in a bore.
• the lever arrangement 15 is T-shaped and arranged, see. Fig. 5 that it acts approximately in the middle between the inlet and outlet ends 11, 12 on the measuring tube 13, whereby this experiences its greatest lateral deflection in the middle.
• the excitation arrangement 16 comprises a first excitation coil 26 and an associated first permanent magnet armature 27 and a second excitation coil 36 and an associated second permanent magnet armature 37.
• the two excitation coils 26, 36 which are preferably connected electrically in series are on both sides of the measuring tube 13 below the yoke 163 on the support frame 14, in particular releasably, fixed so that they interact with their associated armature 27 and 37 during operation.
• the two Excitation coils 26, 36 can, of course, also be connected in parallel with one another, if necessary.
• the two armatures 27, 37 are fixed spaced apart on the yoke 163 in such a way that during operation of the sensor 10, the armature 27 practically from a magnetic field of the excitation coil 26 and the armature 37 practically from a magnetic field Exciter coil 36 passes through and is moved due to corresponding electrodynamic and / or electromagnetic force effects.
• the movements of the armatures 27, 37 generated by the magnetic fields of the excitation coils 26, 36 are transmitted from the yoke 163 and from the arm 154 to the measuring tube 13. These movements of the armature 27, 37 are designed such that the yoke 163 is alternately deflected from its rest position in the direction of the side plate 24 or in the direction of the side plate 34.
• a corresponding axis of rotation of the lever arrangement 15 parallel to the already mentioned measuring tube center axis 13B can e.g. through the boom 154.
• the support frame 14 serving as a support element for the excitation arrangement 16 further comprises a holder 29, which is detachably connected to the side plates 24, 34, for holding the excitation coils 26, 36 and possibly individual components of a magnetic brake arrangement 217 mentioned below.
• the measuring tube 13 can therefore execute torsional vibrations in a first bending vibration torsion mode corresponding to the same direction or in a second bending vibration torsion mode corresponding to the opposite direction.
• the natural fundamental resonance frequency of the second bending vibration torsion mode of, for example, 900 Hz is approximately twice as high as that of the first bending vibration torsion mode.
• a magnetic brake arrangement 217 based on the eddy current principle is integrated in the excitation arrangement 16, which serves to stabilize the position of the mentioned axis of rotation.
• the magnetic brake arrangement 217 it can thus be ensured that the measuring tube 13 always vibrates in the second bending vibration torsion mode and thus any external disturbing influences on the measuring tube 13 do not lead to a spontaneous change into another, especially not in the first, bending vibration torsion mode. Details of such a magnetic brake arrangement are described in detail in US-A 60 06 609.
• the imaginary central axis 13B of the measuring tube is practically slightly deformed and thus spans not a plane but rather a slightly curved surface during the vibrations. Furthermore, a path curve lying in this area and described by the center point of the measuring tube center axis has the smallest curvature of all the path curves described by the measuring tube center axis.
• the excitation arrangement 16 is fed by means of a likewise oscillating excitation current i ec , in particular of adjustable amplitude and of an adjustable excitation frequency f exCl, in such a way that the excitation coils 26, 36 flow through it during operation and in a corresponding manner the Moving the armature 27, 37 required magnetic fields are generated.
• the excitation current i exc is supplied by an operating circuit 50A provided in the measuring device electronics 50 and can be, for example, a harmonic alternating current.
• the excitation frequency f exc of the excitation current i exc is preferably selected in the exemplary embodiment shown here, or it is set such that the laterally oscillating measuring tube 13 oscillates torsionally as exclusively as possible in the second bending vibration torsion mode.
• the measuring sensor 10 further comprises a sensor arrangement 60 which, as shown in FIGS. 2, 3, by means of at least one first sensor element 17 reacting to vibrations of the measuring tube 13, represents a first, in particular analog, measuring signal Si generated.
• the sensor element 17 can e.g. be formed by means of a permanent magnetic armature which is fixed to the measuring tube 13 and interacts with a sensor coil held by the support frame 14.
• sensor element 17 Particularly suitable as sensor element 17 are those which, based on the electrodynamic principle, detect a speed of the deflections of the measuring tube 13.
• acceleration-measuring electrodynamic or also path-measuring resistive or optical sensors can also be used.
• other sensors known to the person skilled in the art and suitable for the detection of such vibrations such as e.g. Strain of the measuring tube 13 sensors are used.
• the sensor arrangement 60 further comprises a second sensor element 18, in particular identical to the first sensor element 17, by means of which it supplies a second measurement signal s 2 , which also represents vibrations of the measuring tube 13.
• the two sensor elements 17, 18 are spaced apart from one another along the measuring tube 13, in particular at an equal distance from the center of the measuring tube 13, in the measuring sensor 10 such that by means of the sensor arrangement 60 both the inlet side and the outlet side Vibrations of the measuring tube 13 are recorded locally and are mapped into the corresponding measuring signals Si or s 2 .
• the first and possibly the second measuring signal Si or s 2 each of which usually has a signal frequency corresponding to the instantaneous oscillation frequency of the measuring tube 13, are, as shown in FIG.
• one of the measuring device electronics 50 preferably digital, evaluation circuit 50B, which serves to determine a measured value X, in particular numerically, which currently represents the process variable to be recorded, here for example the mass flow rate, the density, the viscosity or the pressure, and to convert it into a corresponding measured value signal which can be tapped at the output of the evaluation circuit.
• a measured value X in particular numerically, which currently represents the process variable to be recorded, here for example the mass flow rate, the density, the viscosity or the pressure, and to convert it into a corresponding measured value signal which can be tapped at the output of the evaluation circuit.
• the evaluation circuit 50B is implemented using a microcomputer provided in the measuring device electronics 50, which is programmed in a corresponding manner in such a way that it determines the measured value X on the basis of the measurement signals supplied by the sensor arrangement 60.
• a microcomputer e.g. Both conventional microprocessors and modern signal processors are used.
• both measurement signals Si, s 2 are used in the manner known to those skilled in the art in order to determine, for example, real in the signal-time domain or complex in the signal-frequency domain, a phase difference primarily dependent on the mass flow.
• the process measuring device is also equipped with means which enable compensation of temperature-related influences on the measuring signals Si and / or s 2 used and thus ensure high accuracy of the measured value signal even over a large temperature range and also during a change in the temperature distribution within the measuring sensor ,
• At least one first temperature sensor 40 is also provided in the sensor arrangement 60, which serves to detect a first temperature Ti at a first measuring point in the measuring sensor and to detect one with the same To generate temperature Ti corresponding first electrical, especially continuous, temperature measurement signal ⁇ i.
• the temperature sensor 40 is preferably mounted in the sensor such that the temperature measurement signal ⁇ i supplied in the sensor is correlated as well as possible with a temperature of the process medium, at least when the temperature distribution is stationary within the sensor; At this point it should also be mentioned that the temperature measurement signal ⁇ i preferably represents an absolutely measured first temperature, but possibly also a temperature difference measured relatively with respect to a constant reference temperature.
• the temperature sensor 40 is mounted in the measuring sensor in such a way that it essentially measures a temperature of the measuring tube 13 and supplies a first electrical temperature measurement signal ⁇ i corresponding to this measured temperature.
• the temperature sensor 40 can e.g. be attached directly to the measuring tube 13, but it would then be continuously exposed to its mechanical vibrations, which in turn would cause problems with regard to fatigue strength.
• the temperature sensor 40 is therefore preferably attached to one of the comparatively less vibrating extension pieces 131, 132, here the outlet side of the measuring tube 13.
• a second temperature sensor 41 is provided in the sensor arrangement 60 in order to improve the measuring accuracy and is mounted in the measuring sensor 10 in such a way that it detects a second temperature T 2 at a second measuring point remote from the first measuring point.
• the temperature sensor 41 is arranged according to a preferred embodiment of this development of the invention on an inside of a wall of the sensor housing 100, so that it practically measures a temperature of the sensor housing 100 as the second temperature T 2 .
• the temperature sensor 41 can, for example, also be fixed on the support frame 14.
• temperature sensors 40, 41 within the measuring sensor are to be taken into account and thus there are a multitude of other possibilities for the positioning of the at least one temperature sensor 40 and further temperature sensors that may be provided.
• temperature sensors known to those skilled in the art, in particular previously used in conventional measuring sensors or the like can be used as temperature sensors.
• Temperature-dependent resistors made of metal, for example Pt 100 or Pt 1000, or made of semiconductor material are particularly suitable for the applications mentioned.
• further temperature sensors arranged in the measuring device for example also in the vicinity of the electronics housing, can also be taken into account when compensating for the temperature-related influences on the at least one measurement signal.
• the temperature measurement signals ⁇ -i, ⁇ 2 generated by the temperature sensors 40, 41 and can be tapped from the sensor arrangement 60 are also fed to the evaluation circuit 50B and are thus further processed, in particular to compensate for the Measuring signals s- ⁇ , s 2 , accessible.
• the measurement signal si is first converted into a non-temperature-compensated or also uncorrected intermediate measurement value X 'by means of a measurement stage MS provided in the evaluation circuit 50B. This is then again corrected by means of the evaluation circuit 50B using at least the one temperature measurement signal ⁇ i supplied by the sensor arrangement 60 and thus converted into the measurement value X.
• at least the temperature measurement signal ⁇ 2 likewise supplied by the sensor arrangement 60, is preferably also used to correct the intermediate measurement value X.
• At least one first, analog or digital, correction value Ki for the uncorrected intermediate measured value X derived from the at least one measurement signal Si is determined within a corresponding correction stage KS of the evaluation circuit 50B. Furthermore, the so determined Correction value Ki then, for example, in a simple manner with the uncorrected measured value X, according to the following simple function:
• the correction value Ki formed with the correction stage KS is, as shown in FIG. 6, taking into account the one temperature measurement signal ⁇ i, but preferably taking into account at least the two temperature measurement signals ⁇ i, ⁇ 2 supplied by the sensor arrangement 60.
• At least the temperature measurement signal ⁇ i used for determining the at least one correction value Ki is converted beforehand into a temperature estimate signal ⁇ i.
• the generation of the temperature estimation signal ⁇ i serves to estimate and map as best as possible an instantaneous temperature distribution influenced by the temporal course of the one temperature measurement signal ⁇ i, taking into account not only an instantaneous signal value of the temperature measurement signal ⁇ i, such as in the input mentioned US-A 47 68 384, US-A 56 87 100, WO-A 88 02 476 or WO-A 01 02816, but also based on signal values from the past. Temperature values previously detected by temperature Ti are therefore also taken into account by temperature sensor 40.
• FIG. 7 An example of possible courses of the temperatures Ti, T 2 during a transition range of the time period t 2 -t ⁇ is shown schematically in FIG. 7. If necessary, in addition to the temperature estimation signal ⁇ i, a current signal value of the temperature measurement signal ⁇ i can of course also be taken into account when generating the measured value X.
• G1 0 is a variable or else kept constant, especially but independent of the measured temperatures
• Gn is a weighting function of a signal filter with which that of the
• the correction value Ki can now be determined using the temperature estimation signal ⁇ i using simple, in particular linear, mathematical relationships, such as e.g. the following:
• Estimated signal ⁇ i estimated effective temperature and the first coefficient imparting the correction value Ki which is based on the actually taken into account the first parameter influencing the sensitivity, for example a changing mechanical tension acting axially to the measuring tube 13.
• At least the temperature measurement signal ⁇ 2 is also pre-in corresponding second temperature estimation signal ⁇ 2 , for example on the basis of the following mathematical relationship:
• ⁇ 2 G 20 + G 21 * ⁇ 2 ..., (4)
• Ki 1 + kn ⁇ i + k 12 ⁇ 2 , (5)
• a second correction value K 2 for the uncorrected intermediate measurement value X is determined in addition to the correction value Ki.
• the instantaneous temperature distribution affects, for example, both the modulus of elasticity of the measuring tube 13 and, albeit in a different way, an instantaneous distribution of mechanical stresses within the sensor 10, especially also within the measuring tube 13. Accordingly, this instantaneous temperature distribution also influences its vibration behavior in various ways, for example with regard to the natural resonance frequencies of the measuring tube 13 or also with regard to a ratio between the vibration amplitudes of the useful and Corioli modes.
• the measurement value X is preferably determined in the correction stage on the basis of the value compared to Eq. (1) extended mathematical relationship:
• the conversion of the measurement signal Si into the intermediate measurement value X 'and its combination with the, preferably digital, correction value Ki or the correction values Ki, K 2 has the advantage, among other things, that for this type of determination of the measurement value X on the basis of the intermediate measurement value X 'and the correction values Ki, K 2 practically no essential changes have to be made to the measurement or evaluation methods previously used in conventional process measuring devices of the type described.
• the measured value X can be determined in a simple manner as follows, taking into account a second parameter influencing the sensitivity of the measuring sensor:
• the measuring device electronics comprises a filter stage FS connected upstream of the correction stage KS for temperature measurement signals supplied by the sensor arrangement 60, with at least one first signal filter SFi for the temperature measurement signal ⁇ i, cf. Fig. 6.
• the correction circuit also uses the second temperature estimation signal ⁇ 2
• at least one second signal filter SF 2 is provided in the filter stage FS for the temperature measurement signal ⁇ 2 .
• the signal filters SFi, SF 2 of the filter stage FS are dimensioned and matched to one another, in particular in their filter order and their filter parameters so set that the weight function Gn, G 2 ⁇ defined in each case and the temperature measurement signal ⁇ i folded over it or ⁇ 2 a current temperature distribution within the measuring sensor 10 influencing the measurement signal Si and possibly also the second measurement signal s 2 is simulated or simulated as precisely as possible, taking into account not only current signal values of the respectively fed temperature signal ⁇ i or ⁇ 2 , but also based on signal values from the past of the corresponding temperature signal ⁇ i, ⁇ 2 .
• the signal filters SFi, SF 2 in particular with regard to their signal amplification and their signal delay, but also dimensioned such that the effect of the at least implicitly estimated instantaneous temperature distribution on the sensitivity is taken into account in a compensating manner.
• the weight function Gn of the signal filter SFi is preferably selected such that the temperature estimation signal ⁇ i takes a signal value which is proportional to the instantaneous signal value of the temperature signal ⁇ i in response to a change, for example an increase, in the temperature signal ⁇ i.
• the measuring device electronics 50B will then react to a change in the first temperature measurement signal ⁇ i corresponding to a change in the first temperature with a time delay with a change in the first correction value Ki.
• the weight function Gn can, in addition to a proportionally reinforcing component, also have at least one temporally integrating component of first or higher order.
• the signal filter SF1 can be a low-pass filter, for example.
• the filter arrangements that are actually suitable for the respective sensor type for the signal filters used in the individual case can best be experimentally developed or configured using prototypes of the measuring device experimentally or using computer-aided numerical calculations, e.g. using numerical algorithms using finite elements, determine and optimize.
• the filter parameters that are actually suitable for the respective process measuring device can be e.g. be determined by means of measuring device-specific or measuring device-specific calibration measurements, in particular in connection with computing algorithms which determine the filter parameters numerically and e.g. optimize using the least squares method or generically.
• the first temperature signal ⁇ i supplied by the sensor arrangement 60 is processed in the evaluation circuit before further processing, but in any case before the correction value Ki is calculated, by means of a first A / D converter ADi, as also in FIGS. 7 and 8 are shown schematically, sampled in a time-discrete manner and a first digital signal ⁇ ID is converted.
• this is preferred second temperature signal ⁇ 2 also used is converted into a second digital signal ⁇ 2 D by means of a second A / D converter AD 2 .
• a digital signal filter SF ⁇ D is used as the signal filter for the temperature measurement signal ⁇ i, which implements the following numerical algorithm for the calculation of the temperature estimate signal ⁇ i:
• a second digital signal filter SF 2 D can be used for the temperature measurement signal ⁇ 2 , cf. Fig. 8.
• the digital signal filter SF ID thus implemented is a recursive filter with an at least theoretically infinite impulse response; otherwise the digital signal filter SFID is a non-recursive filter with a finite impulse response.
• the filter stage FS can be used practically completely by means of the aforementioned when using correspondingly powerful microprocessors, especially signal processors Microcomputers and corresponding software can be realized, which also includes the computing algorithms for the digital signal filter. Furthermore, both the determination of the correction value Ki and that of the measured value X can advantageously be achieved by executing correspondingly held computer programs using a microcomputer.
• the measurement signal si or the measurement signals are processed in such a way that the uncorrected measurement value X 'in combination with the at least one correction value Ki delivers the measurement value X with sufficient accuracy.

Priority Applications (2)

Applications Claiming Priority (2)

Publications (2)

Family

ID=32336121

Family Applications (1)

Country Status (6)

Cited By (5)

Families Citing this family (27)

Citations (5)

Family Cites Families (4)

• 2002
  • 2002-12-06 DE DE2002157322 patent/DE10257322A1/de not_active Withdrawn
• 2003
  • 2003-12-02 AU AU2003288210A patent/AU2003288210A1/en not_active Abandoned
  • 2003-12-02 CN CNB2003801052889A patent/CN100374830C/zh not_active Expired - Fee Related
  • 2003-12-02 RU RU2005121257/28A patent/RU2320964C2/ru not_active IP Right Cessation
  • 2003-12-02 EP EP03780099A patent/EP1567834A2/de not_active Withdrawn
  • 2003-12-02 WO PCT/EP2003/013543 patent/WO2004053428A2/de not_active Application Discontinuation
• 2007
  • 2007-10-15 RU RU2007138277/28A patent/RU2007138277A/ru not_active Application Discontinuation

Patent Citations (5)

Also Published As

Similar Documents

Legal Events